Curvature of the penis, called Peyronie's disease, is caused by a buildup of fibrous plaque in the penis. It affects 1 - 4 percent of men. It can cause painful erections, leading to patients withdrawing from sex and becoming depressed. It is most commonly seen in males over 40. You can read a recent study on the drug here and a test of the drug in rat tails -- I kid you not -- here.

BNET's take: Pfizer is spending only $75 million on this deal, which suggests that sales of the drug will be low, due to the small number of patients and their probable resistance to needle-based treatments. So why bother with the deal? Because patients with the condition also suffer from depression and erection problems, and Pfizer has a much bigger franchise in those categories, with Viagra and Zoloft. (Zoloft still sells $135 million per quarter).

Marketing Xiaflex -- with branded or unbranded ads -- will be a good way for Pfizer to drive men to the doctor who are depressed or who have erectile dysfunction of one sort or another, benefitting all three franchises. It's a triple threat for Pfizer because the relevant demo -- men over 40 -- is a target for all three drugs.

Image by Flickr user elsie.esq, CC. UPDATE: The FDA in April 2008 granted Xiaflex priority review for a different condition, Dupuytren's contracture. Ckick here for more.